One of the reactors at the crippled Fukushima Daiichi power plant did suffer a nuclear meltdown, Japanese officials admitted for the first time today, describing a pool of molten fuel at the bottom of the reactor’s containment vessel.

Engineers from the Tokyo Electric Power company (Tepco) entered the No.1 reactor at the end of last week for the first time and saw the top five feet or so of the core’s 13ft-long fuel rods had been exposed to the air and melted down.

Previously, Tepco believed that the core of the reactor was submerged in enough water to keep it stable and that only 55 per cent of the core had been damaged.

Now the company is worried that the molten pool of radioactive fuel may have burned a hole through the bottom of the containment vessel, causing water to leak.
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